Spring actuated liquid propellant gun system

ABSTRACT

A gun system employs liquid oxidizers and fuels instead of the conventional solid propellants. To start a cycle, a propellant chamber is pressurized with liquid propellant to 5,000 PSI. The fluid pressure actuates a piston which is movable within the propellant chamber to automatically compress a spring. The piston is provided with commercial O-ring seals that are capable of withstanding the 5,000 PSI and seal the only opening in the propellant chamber. After pressurization a quick-acting valve is opened, and the spring-biased piston forces the liquid propellant through nozzles and into a combustion chamber where the ensuring combustion launches a projectile. Since the pressure in the combustion chamber equalizes with the pressure in the propellant chamber, the maximum pressure applied to the seals is the 5,000 PSI spring pressure.

Umted States Patent 1191 1111 3,712,171 Sweigart 1 Jan. 23, 1973 1541 SPRING ACTUATED LIQUID 3,479,818 11/1969 Strobl ..60/39.48

PROPELLANT GUN SYSTEM Primary Examiner-Samuel W. Engle [75] Inventor Swe'gart predencksburg AttorneyR. S. Sciascia and Thomas 0. Watson, Jr.

[73] Assignee: The United States of America as ABSTRACT represented by the Secretary of the A gun system employs liquid oxidizers and fuels in- Navy stead of the conventional solid propellants. To start a 22 Filed; N0 1 1970 cycle, a propellant chamber is pressurized with liquid Appl. No.: 89,740

propellant to 5,000 PS1. The fluid pressure actuates a piston which is movable witlhin the propellant chamber to automatically compress a spring. The piston is provided with commercial O-ring seals that are capable of withstanding the 5,000 PS1 and seal the only opening in the propellant chamber. After pressurization a quick-acting valve is opened, and the spring-biased piston forces the liquid propellant through nozzles and into a combustion chamber where the ensuring combustion launches a projectile. Since the pressure in the combustion chamber equalizes with the pressure in the propellant chamber, the maximum pressure applied to the seals is the 5 ,000 PS1 spring pressure.

9 Claims, 3 Drawing Figures PAIENTEDJAHES ma 3.712.171

sum 1 [IF 2 E I i 24 F/G.

INVENTOR. 2 JO/V L. SWE/GART ATTORNEY SPRING ACTUATED LIQUID PROPELLANT GUN SYSTEM STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates generally to improvements in propellant gun systems, and more particularly it pertains to a new and improved spring-actuated liquid propellant gun system wherein the maximum pressure the piston seals will be subjected to is the spring pressure rather than the full pressure produced in the combustion chamber.

In the prior art, liquid propellant guns have been designed using the differential piston technique. Such devices have been unsatisfactory as the O-ring seals are required to seal the full combustion chamber pressure. However, commercial O-ring piston seals are only capable of handling up to 5,000 PSI and therefore cannot withstand the full chamber pressure to which they are subjected. Another problem in the prior art has been the difficulty in providing a sustained pressure during the projectiles internal ballistic path. In operation, as the projectile moves down the gun tube, the volume of the combustion chamber increases, thereby decreasing the overall pressure applied to the projectile.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide a liquid propellant gun system wherein the seals are required to withstand only 5,000 PSI spring pressure.

Another object is the provision of an increased mass flow of propellant to enter the combustion chamber as the projectile moves down the gun tube whereby the pressure driving said projectile is maintained substantially constant.

A further object of the invention is to provide greater gas pressure behind the projectile during its internal ballistic path.

SUMMARY OF THE INVENTION The general purpose of this invention is to provide a spring-actuated liquid propellant gun system which uses liquid oxidizers and fuels instead of the conventional solid propellants normally employed in propellant gun design. To start the cycle, a propellant chamber is pressurized with liquid propellant to 5,000 PSI. The fluid pressure actuates a piston movable within the propellant chamber to automatically compress a spring. The piston is provided with commercial O-ring seals that are capable of withstanding the 5,000 PSI and seal the only opening in the propellant chamber. After pressurization a quick-acting valve is opened and the spring-biased piston forces the liquid propellant through nozzles and into a combustion chamber where the ensuing combustion launches a projectile. At emission of the projectile the quick-acting valve is closed and the cycle is complete.

. net force applied to the piston seals is that produced by the spring.

Moreover, as a result of the force the spring-biased piston applies, the system provides an increasing mass flow of propellant to enter the combustion chamber as the projectile moves down the gum tube. This enables the gas pressure behind the projectile to remain sub stantially constant during its internal ballistic path.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross section of a preferred embodiment of the spring-actuated liquid propellant gun;

FIG. 2 illustrates a section of the device taken on the line 2--2 of FIG. 1 looking in the direction of the arrows; and

FIG. 3 shows a section of the device taken on line 3-3 of FIG. 2 looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1, which illustrates a preferred embodiment of the liquid propellant gun, shows an assembly 10 having an elliptical propellant chamber 12 and a cylindrical combustion chamber 14. A suitable quick-acting valve 16, such as a gate valve, separates chambers 12 and 14. Valve 16 may be mechanically operated, as by a spring (not shown), or electrically operated, as by a solenoid (not shown). With valve 16 closed, liquid propellant is pumped into propellant chamber 112 through a suitable valve 18.

A piston 20 is slidingly mounted within a bore 12a for reciprocation between propellant chamber 12 and combustion chamber 14. A hole 15 is provided in combustion chamber 14 to receive piston 20. As seen in FIG. 2, piston 20 is provided with a concave head or face 21. This is by way of examplle only, as the piston head may have other shapes, such as flat or spherical. The pressurized propellant applies a force to the aft end 23 of piston 20 to move it through hole 15 and into combustion chamber 14. The piston 20 is fixedly attached to two L-shaped connecting rods 22 (see FIG. 2) which reciprocate in paths 25 outside of propellant chamber 12. A circular plate 24 is :mounted at the other end of connecting rods 22. Connecting rods 22 and plate 24 are mounted to reciprocate in a driving chamber within a cylindrical housing 26 and thereby compress a spring 28 against wall] 30 of housing 26. Spring 28 is supported by plate 24 and is situated below piston 20 in the separate housing 26 because of its size and to prevent exposure of the spring to chamber temperature and gases. Commercial O-ring seals 32 are mounted on piston 20 and are capable of withstanding the 5,000 PSI to which the propellant chamber 12 is subjected to.

As seen in FIG. 1 a suitable inlet means, such as nozzles 34, are provided to allow the liquid propellant in propellant chamber 12 to enter combustion chamber 14, when gate valve 16 is opened. Nozzles 34 provide the necessary propellant injection into combustion chamber '14. Combustion chamber 14 is adjacent to and opens into a gun tube 36 in which the projectile 38 to be launched is located.

In operation, to start a cycle, gate valve 16 is closed and liquid propellant is pumped into propellant chamber 12, under pressure, via valve 18. This applies a pressure of 5,000 PS1 to the aft face 23 of piston 20 to actuate it in a forward direction, into combustion chamber 14, and thereby automatically compress spring 28. (Or, of course, in the alternative, spring 28 may be mechanically compressed and liquid propellant then pumped into propellant chamber 12.) After propellant chamber 12 has been pressurized to 5,000 PSI and spring 28 compressed, gate valve 16 is opened. This causes spring 28 to expand and thereby actuate piston 20 in an aft direction to force the pressurized liquid propellant through nozzles 34. As liquid propellant enters combustion chamber 14, the combustion cycle starts. Ifa monopropellant is used, an igniter (not shown) is inserted in combustion chamber 14. If a hypergolic mixture of an oxidizer and fuel is used, a piston system for each could be used with combustion starting at the first contact of the two fluids.

As a result of the propellant being forced into combustion chamber 14 by the recoil of piston 20, the pressure in combustion chamber 14 equalizes with the pressure in propellant chamber 12. in addition, the pressure produced as a result of combustion is transmitted through the propellant in chamber 12 and applied to the aft face 23 of piston 20 as well as being directly applied to the forward face 21 of piston 20. In this manner, equal and opposite pressures are applied to piston 20 and seal 32 since the projected areas of the forward and aft faces are equal. Thus, the resultant driving force and the only net force being applied to seals 32 is the 5,000 PSI produced by the compression of spring 28. The explosive pressure of the combustion process forces projectile 38 out of gun tube 36. At emission of projectile 38, gate valve 16 is closed, thus stopping the cycle.

As a result of spring-loaded piston 20 forcing the pressurized fluid through nozzles 34, it is seen how the invention provides an increasing mass flow of propellant to enter combustion chamber 14 as projectile 38 moves down gun tube 36. The pressure produced by the combustion process is distributed over the continually increasing volume of combustion chamber 14 as the projectile 38 moves down gun tube 36. This increase in volume would normally decrease the effective pressure being applied to projectile 38. However, in the present invention, the increased flow of propellant being forced into combustion chamber 14 by piston 20, maintains a constant pressure in the combustion chamber as its volume increases whereby the effective pressure being applied to projectile 38 is maintained substantially constant'during its internal ballistic path.

One criterion for the liquid propellant gun to function properly is that the nozzle area 34 must be equal to the area of the piston 20. This enables the spring 28 to move at its maximum velocity and increase the velocity of piston 20, which increases the mass flow of the propellant entering combustion chamber 14 as the projectile 38 moves down gun tube 36.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings.

What is claimed is:

1. A liquid propellant gun system comprising:

a housing having a combustion chamber, at least one propellant chamber and at least one driving chamber therein;

a first passageway in said housing connecting said combustion chamber and a first propellant chamber;

a first piston slidingly and sealingly mounted within said first passageway;

said first piston having a forward face exposed to pressure within said combustion chamber and an aft face exposed to pressure within said first propellant chamber, said forward face and said aft face having equal projected areas;

first biasing means within a first driving chamber connected to said first piston for normally biasing said first piston away from said combustion chamber;

first means to force said first piston toward said combustion chamber against the force of said first biasing means;

a second passageway in said housing communicating with said first propellant chamber and said combustion chamber;

first valve means for controlling communication through said second passageway of said first propellant chamber and said combustion chamber; and

a gun tube extending from said combustion chamber.

2. The gun system of claim 1 wherein said first piston has an o-ring seal thereon.

3. The gun system of claim 1 wherein said first biasing means comprises a plate connected to said first piston and movable within said first driving'chamber and a spring means for normally biasing said plate away from said combustion chamber.

4. The gun system of claim 3 wherein said first valve meanscomprises nozzle means to provide injection ofa propellant into said combustion chamber and a gate valve to control flow through said nozzle means.

5. The gun system of claim 4 wherein said first means comprises the pressurized propellant within said first propellant chamber.

6. The gun system of claim 4 wherein said first means comprises mechanical means to compress said first biasing means.

7. The gun system of claim 4 wherein L-shaped connecting rods connect said plate to said first piston.

8. The gun system of claim 1 wherein a third passageway connects a second propellant chamber with said combustion chamber;

a second piston slidably and sealingly mounted within said third passageway, having an upper face exposed to pressure within said combustion chamber and a lower face exposed to pressure within said second propellant chamber; second driving chamber having second biasing means therein connected to said second piston for normally biasing said second piston away from said combustion chamber;

second means to force said second piston towards said combustion chamber against the force of said second biasing means;

a fourth passageway in said housing communicating with said second propellant chamber and said combustion chamber; and

second valve means for controlling communication through said fourth passageway of said second propellant chamber and said combustion chamber.

9. A liquid propellant power plant which comprises:

a housing having a combustion chamber, at least one propellant chamber and at least one driving chamber therein;

a first passage and a second passage both connecting said propellant chamber with said combustion chamber;

a piston slidingly and sealingly mounted within said first passage having a forward face exposed to pressure in the combustion chamber and an aft face exposed to pressure in said propellant chamber;

said forward face and said aft face having equal projected areas;

biasing means connected to said piston for normally urging said piston away from said combustion chamber;

nozzle means within said second passage to provide injection of a propellant from said propellant chamber into said combustion chamber;

valve means to control the flow of propellant through said nozzle means; and

means for urging said piston toward said combustion chamber. 

1. A liquid propellant gun system comprising: a housing having a combustion chamber, at least one propellant chamber and at least one driving chamber therein; a first passageway in said housing connecting said combustion chamber and a first propellant chamber; a first piston slidingly and sealingly mounted within said first passageway; said first piston having a forward face exposed to pressure within said combustion chamber and an aft face exposed to pressure within said first propellant chamber, said forward face and said aft face having equal projected areas; first biasing means within a first driving chamber connected to said first piston for normally biasing said first piston away from sAid combustion chamber; first means to force said first piston toward said combustion chamber against the force of said first biasing means; a second passageway in said housing communicating with said first propellant chamber and said combustion chamber; first valve means for controlling communication through said second passageway of said first propellant chamber and said combustion chamber; and a gun tube extending from said combustion chamber.
 2. The gun system of claim 1 wherein said first piston has an o-ring seal thereon.
 3. The gun system of claim 1 wherein said first biasing means comprises a plate connected to said first piston and movable within said first driving chamber and a spring means for normally biasing said plate away from said combustion chamber.
 4. The gun system of claim 3 wherein said first valve means comprises nozzle means to provide injection of a propellant into said combustion chamber and a gate valve to control flow through said nozzle means.
 5. The gun system of claim 4 wherein said first means comprises the pressurized propellant within said first propellant chamber.
 6. The gun system of claim 4 wherein said first means comprises mechanical means to compress said first biasing means.
 7. The gun system of claim 4 wherein L-shaped connecting rods connect said plate to said first piston.
 8. The gun system of claim 1 wherein a third passageway connects a second propellant chamber with said combustion chamber; a second piston slidably and sealingly mounted within said third passageway, having an upper face exposed to pressure within said combustion chamber and a lower face exposed to pressure within said second propellant chamber; a second driving chamber having second biasing means therein connected to said second piston for normally biasing said second piston away from said combustion chamber; second means to force said second piston towards said combustion chamber against the force of said second biasing means; a fourth passageway in said housing communicating with said second propellant chamber and said combustion chamber; and second valve means for controlling communication through said fourth passageway of said second propellant chamber and said combustion chamber.
 9. A liquid propellant power plant which comprises: a housing having a combustion chamber, at least one propellant chamber and at least one driving chamber therein; a first passage and a second passage both connecting said propellant chamber with said combustion chamber; a piston slidingly and sealingly mounted within said first passage having a forward face exposed to pressure in the combustion chamber and an aft face exposed to pressure in said propellant chamber; said forward face and said aft face having equal projected areas; biasing means connected to said piston for normally urging said piston away from said combustion chamber; nozzle means within said second passage to provide injection of a propellant from said propellant chamber into said combustion chamber; valve means to control the flow of propellant through said nozzle means; and means for urging said piston toward said combustion chamber. 